I/O Buffer Sourcing And Sinking Limit; Bus Loading - RabbitCore RCM4500W User Manual

A.3 I/O Buffer Sourcing and Sinking Limit
Unless otherwise specified, the Rabbit I/O buffers are capable of sourcing and sinking 8 mA of
current per pin at full AC switching speed. Full AC switching assumes a 29.4 MHz CPU clock
with the clock doubler enabled and capacitive loading on address and data lines of less than 70 pF
per pin. The absolute maximum operating voltage on all I/O is 3.6 V.
A.4 Bus Loading
You must pay careful attention to bus loading when designing an interface to the RCM4510W.
This section provides bus loading information for external devices.
Table A-5 lists the capacitance for the various RCM4510W I/O ports.
Parallel Ports A to E
Table A-6 lists the external capacitive bus loading for the various RCM4510W output ports. Be
sure to add the loads for the devices you are using in your custom system and verify that they do
not exceed the values in Table A-6.
Table A-6. External Capacitive Bus Loading -40°C to +85°C
All I/O lines with clock
doubler enabled
User's Manual
Table A-5. Capacitance of Rabbit 4000 I/O Ports
I/O Ports
Clock Speed
Output Port
Input
Capacitance
(pF)
12
Maximum External
(MHz) Capacitive Loading (pF)
29.49
Output
Capacitance
(pF)
14
100
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